Add nsIGfxInfo::GetMonitor support for Linux. (bug 1175005 part 4, r=…

…nical)

widget/GfxInfoX11.cpp

@@ -14,6 +14,7 @@
 #include "prenv.h"
 
 #include "GfxInfoX11.h"
+#include "mozilla/X11Util.h"
 
 #ifdef MOZ_CRASHREPORTER
 #include "nsExceptionHandler.h"
@@ -534,6 +535,34 @@ GfxInfo::GetIsGPU2Active(bool* aIsGPU2Active)
   return NS_ERROR_FAILURE;
 }
 
+nsresult
+GfxInfo::FindMonitors(JSContext* aCx, JS::HandleObject aOutArray)
+{
+#if defined(MOZ_WIDGET_GTK)
+  // No display in xpcshell mode.
+  if (!gdk_display_get_default()) {
+    return NS_OK;
+  }
+#endif
+
+  // Note: this doesn't support Xinerama. Two physical displays will be
+  // reported as one monitor covering the entire virtual screen.
+  Display* display = DefaultXDisplay();
+  Screen* screen = DefaultScreenOfDisplay(display);
+
+  JS::Rooted<JSObject*> obj(aCx, JS_NewPlainObject(aCx));
+
+  JS::Rooted<JS::Value> screenWidth(aCx, JS::Int32Value(WidthOfScreen(screen)));
+  JS_SetProperty(aCx, obj, "screenWidth", screenWidth);
+
+  JS::Rooted<JS::Value> screenHeight(aCx, JS::Int32Value(HeightOfScreen(screen)));
+  JS_SetProperty(aCx, obj, "screenHeight", screenHeight);
+
+  JS::Rooted<JS::Value> element(aCx, JS::ObjectValue(*obj));
+  JS_SetElement(aCx, aOutArray, 0, element);
+  return NS_OK;
+}
+
 #ifdef DEBUG
 
 // Implement nsIGfxInfoDebug

widget/GfxInfoX11.h

@@ -48,6 +48,8 @@ class GfxInfo final : public GfxInfoBase
 
   NS_IMETHOD_(void) GetData() override;
 
+  nsresult FindMonitors(JSContext* cx, JS::HandleObject array) override;
+
 #ifdef DEBUG
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_NSIGFXINFODEBUG